This invention relates generally to safety apparatus for concrete mixers. More particularly, this invention relates to apparatus for controlling the closing force of a flip chute portion of a concrete discharge chute.
An apparatus commonly used to discharge concrete from a concrete mixer such as one carried by a concrete mixer truck is referred to as a xe2x80x9cdischarge chutexe2x80x9d. The discharge chute is mounted at a discharge end of the concrete mixer, and is basically an upwardly opening channel extending from the discharge end for guiding the flow of concrete being discharged.
In order to achieve a workable compromise between having as long a chute as possible without having interference from the chute when it is not required, such as during transport of the concrete mixer, discharge chutes are generally made collapsible.
A common way of making the discharge chute collapsible is to make it of two hingedly connected sections, which may be placed end to end in a xe2x80x9cworking positionxe2x80x9d for discharge and placed one above the other into a xe2x80x9cstored positionxe2x80x9d. The two parts of the discharge chute are referred to as the xe2x80x9cmain chutexe2x80x9d and the xe2x80x9cflip chutexe2x80x9d. The main chute is the first run of the discharge chute adjacent to the discharge end of the concrete mixer and that part of the discharge chute typically mounted to the concrete mixer (or structure supporting the concrete mixer). The flip chute is the second or lower run of the discharge chute hingedly connected at an upper edge to an upper edge of the main chute so as to be pivotal through an arc of approximately 180xc2x0 between the stored position and the working position.
Like the main chute, the flip chute is typically a steel construction and of significant mass. The pivoting of the flip chute is commonly a manual operation and its weight generally maintains it in both the stored and the working positions.
As the flip chute is pivoted or rotated from the stored position to the working position, it would normally begin to fall after its centre of gravity passes a transverse hinge axis about which the hinge pivots. If not guided by an operator it will fall until fully open (ie. in the working position) at which time the flip chute and the main chute engage with sufficient force to create a severe pinch zone. The pinch zone poses a significant safety risk and has resulted in hand injuries resulting in loss of fingers.
It is an object of the present invention to provide a safety mechanism for counteracting the closing force of the flip chute as it approaches the working position to reduce the pinching force in the pinch zone.
It is a further object of the present invention to provide an assist mechanism to reduce the force required to initiate movement of the flip chute away from its stored position.
In very general terms, the present invention provides apparatus for generating a moment of desired direction and amount about the hinge axis to reduce the moment which would otherwise be caused about the hinge axis by the weight of the flip chute acting through its centre of gravity.
A flip chute safety and assist mechanism is provided for a flip chute hingedly connectable to a main chute for movement about a transverse hinge axis between a stored position over the main chute and a working position as an extension to the main chute, through an over centre position. The mechanism has a first member rigidly securable to the flip chute to extend away from the hinge axis and rotate with the flip chute about the hinge axis. The mechanism further has biasing means connectable to the first member and to the main chute to generate a moment about the hinge axis contra to a moment generated by the weight of the flip chute as the flip chute approaches its working position.
The biasing means may be connectable to the first member and to the main chute to generate a moment about the hinge axis contra to a moment generated thereabout by the weight of the flip chute.
The first member may be a lever and the biasing means may include a spring.
The spring may be connected to the lever by a cable connected at one end to the spring and at an opposite end to the lever.
The mechanism may include a guide wheel for engaging and locating the cable, the guide wheel being rotatably mounted to a guide wheel bracket securable to the main chute.
The biasing means may include an adjuster for varying the tension exerted on the lever by the spring. The adjuster may include an anchor securable to the main chute and an adjustable length link for connecting the spring to the anchor. The adjustable length link may include a rod threadedly engaging a tube.
A foldable chute is also provided having a main chute, a flip chute hingedly connected to the main chute for movement about a transverse hinge axis between a stored position over the main chute and a working position as an extension to the main chute, through an over centre position wherein the centre of gravity of the flip chute is above the hinged axis. The foldable chute further includes a safety and assist mechanism connected thereto in accordance with the flip chute safety and assist mechanism described above.